Method and apparatus for cooling strip



Dec. 6, 1966 J. w. OBRIEN 3,289,449

METHOD AND APPARATUS FOR COOLING STRIP Filed May 20, 1964 2 Sheets-Sheet l INVENTOR. JEREMIAH W. O'BRIEN HI ATTORNEY Dec. 6, 1966 J- W. OBRIEN METHOD AND APPARATUS FOR COOLING STRIP Filed May 20, 1964 2 Sheets-Sheet B INVENTOR. JEREMIAH W. OBRIEN HIS ATTORNEY United States Patent 3,289,449 METHGD AND APPARATUS FQR CUQLING STRIP Jeremiah Wagner tillrien, Pittsburgh, Pa, assignor to United Engineering and Foundry Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed May 20, 1964, Ser. No. 368.935 Claims priority, application Great Britain, June 4, 1963, 22,14ll/ 63 4 Claims. Cl. 72-20l) This invention relates to a method and an apparatus useful in the operation of a hot strip rolling mill and, more particularly, to a cooling system for controlling the temperature of the strip as it issues from the last stand of the finishing train but prior to its being coiled.

In the manufacturing of hot metallic strip it is quite important, for metallurgical purposes, that the temperature of the strip be controlled prior to its being reduced to its final thickness in the hot strip mill and subsequent to its leaving the mill, but prior to its being coiled.

With reference to the control of the temperature of the strip after it leaves the mill, for example in rolling low carbon steels to a range of .050 to .25 inch, generally the proper finishing temperature of the strip emerging from the last stand of the mill is above 1550 F. This finishing temperature is generally employed over the aforesaid range of stripthicknesses in the operation of most modern mills at normal maximum rolling speeds. In order to reduce the temperature of the strip prior to its being coiled, present day mills are provided with runout tables located after the last rolling mill stand which is made long enough and equipped with enough quenching spray stations to cool a strip betwen the range of 200500 F. below the finishing rolling temperature. In the rolling of low carbon steels it is generally the normal practice to coil the strip at a temperature within the range of 1200 to 1300 F. While in given cases one or all of this range may vary, it prevails for a large part of the products rolled by a modern hot strip mill.

The strip is usually cooled as it passes along the runout table and prior to its being coiled by a plurality of water spray stations or banks located above and below the strip, it being customary for obvious reasons to supply a greater proportion of the water from above the strip than from below. The present mechanism for thus cooling of strip usually includes a spraying system which has a fixed transversal field of water coverage commensurate with the maximum width of strip that the mill is capable of rolling. As a result, when strip narrower than the maximum width is rolled, there is a considerable waste of water, which condition becomes worse as the strip width narrows. It must be pointed out that the cost of water is considerable, so that it is quite important to use it judiciously. In addition to the waste involved, the system must be designed to deliver the necessary volume to effectively cool the narrow strip when rolling at the maximum speed of the mill, which adds substantially to the cost of the system.

With reference to the aforesaid statement that normally wider strip is rolled at a lower speed than narrow strip, it may be well to give the reason for this practice. The explanation lies in the desire to reduce the capital expenditure of the mill. Accordingly, the mill arrangement is not designed or powered to roll the maximum width strip at the maximum speed. As a result, the wide product is rolled at a speed less than the maximum speed of the mill and commensurate with the particular power demands for the reduction desired.

In addition to this disadvantage, in the more modern mills, the cooling of a strip on the runout table has presented some erious problems. For example, in a recent installation of a hot strip mill having a maximum speed EidhAl-d Patented Dec. 6, 1966 of the order of 3,000 f.p.m., the water spray system necessary to obtain the desired cooling was designed to deliver approximately 20,000 gal. per minute to the sprays arranged above the runout table and approximately 4,000 gal. per minute to the sprays arranged below the runout table. It goes without saying that a system for supplying such a volume of water is quite expensive in a number of ways.

Since the new mills now being erected will have a maximum speed of 3800 f.p.m., an even greater quantity of water is necessary to ellect proper strip cooling. In addition to the costly water supply system necessary for these high speed mills, it must be pointed out that in employing the present day spray system, it is necessary to provide a substantially longer spray section and, consequently, a much longer runout table, both of which factors greatly increase the capital expense incident to the manufacturing and installing of the cooling system.

The present invention is addressed to a temperature control method and apparatus for use with a rolling mill that will alleviate each of the aforesaid disadvantages. One object of the present invention is addressed to a method and apparatus for controlling the fluid output of the coolant delivery members in a manner that full benefit is received from the cooling media, notwithstanding the fact that a wide range of varying width and thickness work pieces are to be rolled.

Another object of this invention is to provide a coolant system for employment with a hot runout table of a hot strip mill, the sprays of which will be regulated pursuant to the width or speed of the mill so that when the maximum width strip is being rolled at a first speed, the field of spray will extend to the opposite sides of the strip and perpendicular to the center line of the strip and when the minimum width strip is being rolled at a second speed, the sprays will be positioned in an oblique relationship with respect to the center line of the strip, whereby the surface of the strip will be subject to a different amount of water than when the sprays are positioned for the maximum width strip. For strip possessing width between the maximum or minimum, the sprays will be adjusted to suit the particular width.

Another object of the present invention is to provide a method of and apparatus for regulating the position of the spray fields of the spray system commensurate with the change in speed of the mill. For example, the fields of sprays may be longer than the particular width strip being rolled so that the fields of sprays overhang the edges of the strip when it is being rolled at a slow speed, and when the speed is increased, the fields of the sprays will be positioned to expose the strip to greater unit coverage of the fields. Thus, as the speed gradually increases, the spray system is changed accordingly, to gradually expose the strip to more unit coverage of the fields of sprays.

Another method of operating the cooling system where the speed of the mill during the rolling of the strip is to be increased, would be to make the fields of sprays to equal to the width of the maximum strip and then to compensate for the increase of the speed by adding additional sprays as the speed increases. In this case, for strip of widths less than the maximum the position of the fields of sprays can be changed to compensate for the increases in speed or in combination therewith, additional sprays can be added.

A still further object of the invention has reference to providing means whereby the position of the fields of the sprays may be automatically adjusted by means which is responsive to the speed of the strip or the width of the strip.

In one form of the present invention, there is provided in conjunction with the hot runout table of the hot strip mill, a strip cooling system comprising means for positioning the fields of the sprays thereof, whereby these fields will be kept within the edges of the strip of various width strips to thus gain the maximum benefit from and alleviate any waste of the coolant.

These objectives and advantages as well as others, will be more fully understood when the following specification is read in light of the accompanying drawings of which:

FIGURE 1 is a schematic elevational view showing the last stand of the finishing train of a hot strip mill, its runout table, together with a strip cooling system and coiler;

FIGURE 2 is a plan view of a portion of the hot runout table shown in FIGURE 1 illustrating a spray system built in accordance with the present invention;

FIGURE 3 is a partial sectional view of the apparatus shown in FIGURE 2; and

FIGURE 4 is a diagrammatical view illustrating two varying width strips and the positions of the fields of the sprays for these strips.

With reference to FIGURE 1 there is illustrated schematically the last stand ll) of a hot strip finishing train in which the final reduction of the strip is taken, the strip S passing from the stand It), as indicated by the arrow, to a hot runout table 11 which includes banks of fluid or Water sprays l2 and strip side guards 13. At the extreme right-hand side of the table 11, as one views FIGURE 1, a down-coiler 14 is arranged for receiving the strip issuing over the table, which has the usual pinch roll assembly 15 arranged above it. The stand 10 includes a motor 16 having a speed regulator 17 and entry and delivery side guides 13. For the guides 18, at the left of the stand 10, there is provided traversing means 19 including a motor 20. The side guards 13 are also provided with traversing means 21 including a motor 22. All of these elements, except for the strip spray system are well known and do not believe to warrant a detailed description.

As previously noted, FIGURES 2 and 3 illustrate a portion of the runout table and one of the longitudinal banks of the spray system built in accordance with the present invention. As shown, the runout table 11 includes a plurality of spaced-apart rollers 23 each having individual motors 24. Above the rollers 23, as shown in FIGURE 3, there is positioned a number of spaced-apart arcuately shaped pipes 25, which are secured to a common horizontally extending fluid supply pipe 26, the fluid supply pipe being rotatably received in a bearing stand 27, the base of which is secured to the foundation as shown in FIGURE 3. As shown in FIGURE 2, at one end of the supply pipe 26, there is provided a swivel joint 28 to which is connected an input pipe 29, the swivel joint 23 permitting the supply pipe 26 to rotate relative to the input pipe 29.

To the other end of each of the arcuate shaped pipes 25, there is a horizontal pipe 30 which interconnects the top ends of the pipes and receives the fluid passing through them. As shown in FIGURE 3, at the underside portion of the pipe at relatively short equal distance, spaced-apart positions, there is provided a number of small diameter pipes 31, the lower ends of which are secured to rotatable joints 32. To the lower ends of the rotatable joints 32, there is provided nozzles 33, which in the preferred embodiment are designed to give fields of sprays which are characterized by being relatively narrow in one direction and relatively wide in the other, or what may be referred to as a fiat spray. The contour of these fields of sprays is examplified in FIGURE 4.

For each spray assembly, just below the rotatable joints 32 there is provided a link 34 which is connected to a cross bar running substantially parallel to the pipe 3i and which through the interconnecting relationship rotates the nozzles 33 in unison. The links 34 and cross bar 35 are best shown in FIGURE 2. To one of the links 34, an arm 36 is secured, as shown in FIGURE 3 and to this arm an actuating rod 37 is connected, the rod 37 running in a direction parallel to the pipes 25 when viewed in FIGURE 2. The actuating rod 3'7 is secured to the gear of a worm-wheel jack 38, the jack being operated by an electric motor 39, shown only in FIGURES 2 and 3. As illustrated in phantom in FIG- URE 3, the entire spray assembly is adapted to be pivoted about the axis of the supply pipe 26 relative to the bearing stand 27 for which reason a piston cylinder assembly 40 is provided, the piston of which is secured to a cross beam 41 which, in turn, is secured to each of the pipes 25, the cylinder being only seen in FIGURE 3.

In briefly explaining the operation of the aforesaid apparatus, reference is made to FIGURE 4 where there is diagrammatically shown two ditierent width strips, designated A and B, which for the purposes of discussion will be understood to represent the maximum and minimum width strips, respectively produced by the stand 10. In cooling the strip A, it will be noted that the fields of sprays represented by the reference character 42 are arranged so that they fall within the opposite edges of the strip A, thereby equal cooling of the surface thereof will be assured. When the mill is rolling a strip of the width illustrated by strip B, the fields of sprays 42 will be so arranged so that their extreme ends will fall within the opposite edges of the strip B, whereby full advantage of the cooling sprays will be again realized.

As previously mentioned, when the stand 10 is rolling strip of the width A, its speed may be considerably lower than when it is rolling the narrower strip B. Consequently, when the mill is rolling the maximum width strip A, the fields of the sprays will be positioned so that the unit area of spray coverage will be at a minimum, but yet in view of the longer length of time involved in the strip passing under the sprays, sufiicient cooling is assured and that without any waste of water. When the minimum width strip B is being rolled, the fields of sprays are positioned to expose the strip to a maximum amount of water so that while the strip may be traveling under the sprays at the maximum speed, this is compensated for by the increase spray coverage and again, eifective cooling is assured without any waste of water.

As previously mentioned, and as shown on FIGURE 1, the motor 39 that regulates the angular position of the nozzles 33 can be electrically connected to the traversing means 19 of the mill side guides 18 and/or to the traversing means 21 for the side guards 13 whereby the fields of sprays 42 can be automatically adjusted when the mill side guides 18 or the runout table strip guards 13 are adjusted for a new width of strip, this being done by the operation of the motor 29 of the strip guide 18 or the motor 22 of the side guards 13.

In this regard and with reference again to FIGURE 4, in referring to the strip S, should it be desirable to adjust the fields of the sprays 42 in accordance with the change in speed of the mill, it will be noted that the cooling effect could be increased by simply rotating the fields 42 to control the amount of fluid discharged onto the strip. In this manner in the rolling procedure where the speed of the fininshing train is gradually increased to reduce the end-to-end temperature difference of the strip in accordance with recently inaugurated practice, the fields of the sprays 42 can be positioned so that the fields overhang the edges of the strip. Ailternately, as previously mentioned, the lengths of the spray fields can be made equal to the width of the maximum strip, in which case the speed increase is compensated for by opening the valves such as the valve shown in FIGURE 2 of additional spray banks. In the first case, when the leading end of the strip passes under the nozzles 33 and as its speed is gradually increased, the fields of sprays can be rotated so as to progressively increase more and more of the strip surfaces to the water delivered by the spray system. In this connection, as indicated in FIGURE 1, the motor 39 of the spray system can be electrically correlated to the speed of the strip, say for example, by use of the speed control unit 17 associated with the motor 16 of the stand 10. In this way, as the mill speed increases, the motor 39 would operate to arrange the fields of sprays 42 in the proper position.

It will be appreciated that FIGURES 2 and 3 have illustrated but one form of a spray system and a mechanism for moving the sprays in unison so as to keep the fields of sprays 462 at all times parallel to each other, and various other means can be employed for carrying out the features of the present invention. In certain mill arrangement, the present method and apparatus may be employed in conjunction with the entry table of the finish ing train of a hot strip mill or the delivery table of the last roughing stand thereof.

While no particular comment has been made of it, it will be appreciated that the usual bottom spray systems will be also employed. Also, it will be appreciated that in place of the nozzles 33, the coolant may be supplied by long pipes, a trough or a laminar spray system.

In accordance with the provisions of the patent statutes, I have explained the principle and operation of my invention and have illustrated and described what I consider to represent the best embodiment thereof. However, I desire to have it understood that within the scope of the appended claims, the invention maybe practiced otherwise than as specifically illustrated and described.

I claim:

1. In a method of cooling within a desired range of temperatures heated metallic workpieces, such as strips, by passing the strips through a field of coolant incident to their being rolled.

said strips capable of possessing different characteristics, such as, varying widths, thicknesses, and speeds of travel, and

wherein the field of coolant is longer than the width of the maximum strip, comprising the steps of:

arranging the field of coolant so that the field extends over the opposite sides of the strips when the strips are traveling at a first speed,

changing the position of the field of coolant to increase the area of the field as the speed of the strip increases relative to said first speed so that the strip is subject to a substantial uniform temperature about its entire length.

2. An apparatus for cooling heated metallic workpieces, such as strips, said strips having varying characteristics that efiect their thermal conditions as they issue over a predetermined path, comprising:

a plurality of coolant discharge members arrange over the path of the strip,

means for supporting said coolant discharge members in a relationship to produce a field of coolant across the strips,

means for adjusting the members in a manner so that the field of coolant may be displaced relative to the strips to compensate for a change in the cooling rate of the strips caused by a change in the characteristics thereof,

said means for adjusting the member being connected to two or more of the members thereby the members are adjusted in unison, and

strip width determining means controlling the means for adjusting the discharge member to adjust said member pursuant to a change in the width of the strip.

3. An apparatus for cooling heated metallic workpieces, such as strips, said strips having varying characteristics that effect their thermal conditions as they issue over a predetermined path, comprising:

a plurality of coolant discharge members arranged over the path of the strip,

means for supporting said coolant discharge members in a relationship to produce a field of coolant across the strips,

means for adjusting the members in a manner so that the field of coolant may be displaced relative to the strips to conmpensate for a change in the cooling rate of the strips caused by a change in the characteristics thereof,

said means for adjusting the member being connected to two or more of the members thereby the members are adjusted in unison, and

means for adjusting the speed of the mill controlling the means for adjusting the discharge member to adjust said member pursuant to a change in the speed of the mill.

4. In a strip cooling station of a hot strip mill, said station located between the last rolling mill and the means for receiving the strip from the mill comprising:

a table over which the strip passes from the mill,

a support means having a base on one side of the said table and having a portion adapted to overhang a strip supported by said table,

a coolant header carried by the overhung portion of said support means and extending in a direction generally parallel to the direction of travel of said strip,

a plurality of space orifice members rotatably carried by said header,

said members constructed to form elongated fields of coolant on the adjacent surface of a passing strip and generally transverse to its direction of travel,

means for delivering coolant medium to said. header for discharge from said orifice members onto a strip,

means for interconnecting said members so as to effect rotation of the members in unison, thereby to change the position of said fields relative to the surface of said strip.

References Cited by the Examiner UNITED STATES PATENTS 2,696,823 12/ 1954 Scott 134-422 2,851,042 9/1958 Spence 266-6 3,151,197 9/1964 Schultz 266-6 CHARLES W. LANHAM, Primary Examiner. H. D. HOINKES, Assistant Examiner, 

2. AN APPARATUS FOR COOLING HEATED METALLIC WORKPIECES, SUCH AS STRIPS, SAID STRIPS HAVING VARYING CHARACTERISTICS THAT EFFECT THEIR THERMAL CONDITIONS AS THEY ISSUE OVER A PREDETERMINED PATH, COMPRISING: A PLURALITY OF COOLANT DISCHARGE MEMBERS ARRANGE OVER THE PATH OF THE STRIP, MEANS FOR SUPPORTING SAID COOLANT DISCHARGE MEMBERS IN A RELATIONSHIP TO PRODUCE A FIELD OF COOLANT ACROSS THE STRIPS, MEANS FOR ADJUSTING THE MEMBERS IN A MANNER SO THAT THE FIELD OF COOLANT MAY BE DISPLACED RELATIVE TO THE STRIPS TO COMPENSATE FOR A CHANGE IN THE COOLING RATE OF THE STRIPS CAUSED BY A CHANGE IN THE CHARACTERISTICS THEREOF, SAID MEANS FOR ADJUSTING THE MEMBER BEING CONNECTED TO TWO OR MORE OF THE MEMBERS THEREBY THE MEMBERS ARE ADJUSTED IN UNISON, AND STRIP WIDTH DETERMINING MEANS CONTROLLING THE MEANS FOR ADJUSTING THE DISCHARGE MEMBER TO ADJUST SAID MEMBER PURSUANT TO A CHANGE IN THE WIDTH OF THE STRIP. 